DEPL — Base64 encoding

in the last telecon, there was some concern about the MIME
reference, which is used from the XML mapping, which explains,
"For convenience, if the data type is a sequence or array of
octet, the value is represented by a single SimpleValue
element that holds, in the value attribute, the data in
Base64 encoding."

An alternative would be to add a new "BinaryValue" element to
the DataValue element; the BinaryValue could then be declared
to have the "base64Binary" type that is predefined by the XML
Schema spec. The one argument in favor of that is that we could
then depend on XML to define that element's contents (rather
than referencing MIME separately).